Silicone rubbers offer a unique set of desirable physical properties, such as excellent weatherability, ozone resistance, thermal stability, lubricity, and low temperature properties. However, because of their poor mechanical properties, silicone rubbers have traditionally been used in a only limited number of applications. Blends of silicone rubbers with diene rubbers which exhibit good mechanical properties as well as the highly desirable properties of silicone rubbers could be prepared and would be valuable in numerous applications if the rubbers in such blends could be co-cured with sulfur curatives. However, conventional silicone rubbers cannot be cured with sulfur curatives and for this reason in the past the possibility of making and covulcanizing such blends has been precluded.